liUHAB f ILIUBIG SLOBK 



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LIBRARY OF CONGRESS. 

®|Hjt init^rigll 1|o 



UNITED STATES OF AMEEICA. 



THE EARTH, 



•AND- 



ITS RELATIONS TO THE SUN AND MOON, 



AS ILLUSTRATED BY 



Kendall's Lunar Telluric Globe. 

By JOHN S. KENDALL, M, A. 



\ 



NATIONAL SCHOOL FURNITURE COMPANY, 

34 & 36 Madison St., Ch cago, 

18S0. 



^ 



CoPYPwiGHTED 1880, bv Jno. S. Kendall. 



S. I. BRADBURY & SONS, 

PRINTERS, 

78 Fifth Ave., Chicago, 111. 



0NOHUE\^fel\ 




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TABLE OF CONTENTS. 



Page. 

The Sun 7 

The Earth 10 

The Moon , 12 

Ecliptic and Zodiac 14 

To Set Up the Lunarian 15 

To Set Up the Tellurian 16 

1. Comparative Sizes of the Sun, Earth and Moon 19 

2. Revolution of the Moon around the Earth 19 

3. Phases of the Moon 21 

4. Eclipses of the Sun 23 

5. Eclipses of the Moon 25 

6. Tides „ 27 

7. Orbit of the Moon, and its Passage Monthly Through 

the Zodiacal Signs 32 

8. Annual Movement of the Earth Around the Sun 34 

9. Parallelism of the Poles of the Earth 35 

10. Plane of the Ecliptic Parallel to the Plane of the 

Earth's Orbit 36 

11. Winter Solstice 37 

12. Summer Solstice 37 

13. Tropic of Cancer. 38 

14. Tropic of Capricorn 38 

15. All Points between the Tropic of Cancer and Tropic 

of Capricorn ( Torrid Zone ) pass under the Ver- 
ticalRays of the Sun twice each year 39 

16. No Point of the Earth's Surface without the Torrid 

Zone ever Receives the Sun's Vertical Rays 40 



TABLE OF CONTENTS. 

Page. 

17. Equal Length of Day and^Night on the Equator at 

all seasons rr, 41 

18. Longer Days and Shorter Nights during Summer 

North of the Equator, and the Reverse South of 
the Equator 41 

19. Shorter Days and Longer Nights during Winter 

North of the Equator, and the Reverse South of it.. 43 

20. Six Months Day and Six Months Night at the Poles.. 44 

21. The Passage of the Earth Yearly Through the Signs 

of the Zodiac 45 

22. The Apparant Passage of the Sun Yearly Through 

the Sign of the Zodiac 46- 

23. Change of Seasons 47 

24. Vernal and Autumnal Equinoxes 52 

25. Precession of the Equinoxes 53 

26. Siderial Time 55 

27. Solar Time 56 

28. Mean or Clock Time 58 

29. Difference in Time at Different Points on the Earth's 

Surface 58^ 

80. An Independent Ecliptic, showing that the Rotation 
of the Earth on its Axis, moves the Points at 
which the Ecliptic crosses the Equator entirely 
around the Earth at each Revolution ^ 58 

31. The Reason the Sun shines on the North Side of 

Buildings in the Summer Season in our Latitude.. 59 

32. The Reasons for the Division of the Earth's Surface 

into 5 Zones — 2 Arctic, 2 Temperate and 1 Torrid... 60 

33. The Arrangement of an Axis for the Earth perpen- 

dicular to its Orbit, showing the Sun always over 
the Equator, distinguishing the Change in Sea- 
sons, &c 61 

34. Mechanism of the Globe 62 

Declination , 6S 



PREFACE. 

The design of this little work, is to furnish the Teacher a 
key to the proper method of illustrating the more impor- 
tant phenomena connected with the Earth's motions, and 
its relations to the Sun, its own satellite and other planets. 

The necessity of such a work became evident from nu- 
merous requests for an explanation of my method of show- 
ing the precession of the Equinoxes, Solar and Siderial 
time, etc., in connection with the Lunar Telluric Globe. 
In reply to all such inquiries I have written this guide, 
aiming to make the explanations in simple language, and 
free from mathematical discussions. 

Our limits will allow only a glance into the field of astro- 
nomical research, but if it familiarizes the Teacher with 
the proper methods of handling the Globe, I feel confident 
it will stimulate a more thorough and exhaustive reading 
of the works at hand on this most interesting subject. 

1 have used data from the works of Profs. Newcomb, 
Loomis, Chauvenet, Proctor, and others. 



THE SUN. 

The Sun is the central body of the planetary 
system, and the great soui'ce of heat and hght. 
It is a globe of 888,842 miles in diameter, or 
nearly 3.7 times the distance of the Moon from 
the Earth. Its mean distance from the Earth 
is about 92,808,000 miles. Its volume is 1,415,' 
225 times that of the Earth. Its weight is about 
354,936 times that of the Earth. A body weigh- 
ing 100 pounds here would weigh 2,790 pounds 
on the surface of the Sun. By reason of 
the revolution of the Earth in its orbit the 
Sun has an apparent motion among the stars 
from west to east along the great circle of the 
Echptic, making a complete circle of the heav- 
ens in 365 days, 6 hours and 9 minutes. It has 
three true motions, 

1. A revolution on its axis in 25d, 8h, 9m, the 
axis being inchned to the Echptic 7^ 9^; 

2. A revolution in a small orbit, around a 
point which is the common centre of gravity of 
the Sun and the planets revolving about it; 
this point is always within the Sun's volume; 



8 Kendall's lunak tellueic globe. 

3. A progressive moyement tliroiigh. space in 
tlie direction of the constellation Hercules. 

When the Sun is examined through a tele- 
scope its surface is often found marked with 
dark spots. These vary in size and duration, 
seldom lasting longer than six weeks, and 
sometimes only a few hours. These Sun spots 
furnished important data for the computation 
of the time of the Sun's axial revolution. 

The physical constitution of the Sun is 
largely a matter of speculation. At the occur- 
rence of a total echpse of the Sun, wonderful 
clouds of light are observed shooting out 
from its surface in all directions, in irregular 
masses, at some points thousands of miles in 
height. This is called the corona. In sub- 
jecting this light to spectrum analysis it is 
found to consist of some form of exceedingly 
rare gaseous matter, not known on our planet ; 
and this gas, whatever it is, exists at a height 
not less than a milhon of miles above the solar 
surface. Below this corona is the surface or 
layer, called the ^' chromosphere," a mass of un- 
condensed gases, the lower portion containing 
all the gases which compose the Sun's body, and 
the upper having a large proportion of hydro- 
gen. The visible surface of the Sun is beneath 
the chromosphere, and is called the photo- 



Kendall's lunae tellueic globe. 9 

sphere, which is composed of clouds of solar 
gases cooled and condensed by radiation into 
space. The view of this photosphere through 
rifts or openings through the cloiid-like chro- 
mosphere, accounts for the sun spots. This 
photosphere is estimated at 10,000 miles in 
thickness. Inside the photosphere we have 
the enormous interior globe 860,000 miles 
in diameter, composed of hot compressed gases. 
The pressure on this mass of gas is so great 
that it is as dense as a hquid, while the tem- 
perature is so high that no chemical action is 
possible. 

The supply of heat and light which the Sun 
is continuaUy giving off, can be explained sat- 
isfactorily on the theory of contraction in its 
mass. Knowing the amount of energy the 
Sun expends each year, it is estimated that 
with its present magnitude its whole diameter 
need contract but 220 feet a year to produce all 
the heat which it radiates. 

The elements known to exist in the Sun, are : 

Sodium, Magnesium, Nickel, Cadmium, 

Calcium. Iron, Zinc, Cobalt, 

Barium, Chromium, Strontium, Hydrogen, 

If the Sun were removed to the distance from 
xis that the nearest fixed star is estimated to 
be, it would appear as a star of the fifth or sixth 
magnitude. 



10 Kendall's lunak tellueic globe. 

THE EAETH. 

The physical structure of the Earth is the 
special province of Geography, and it is so 
fully treated in all works on this subject now 
in use as text-books in our schools, that we 
shall consider here, the subject of the Earth as 
one of che Planets. 

Traversing the Zodiac in their respective 
orbits, between us and the Sun are the planets 
Mercury and Venus. The former at a mean 
distance from the Sun of 35| milhons of miles, 
and completing a revolution about the Sun in 
88 days; the latter is at a mean distance from 
the sun of 66| milhons of miles, and occu^pjring 
about 225 days in revolving around the Sun. 
The Earth, the third planet, is an average dis- 
tance of 92J milhons of miles from the Sun, and 
occupies 365 d. 5 h. 48 m. 48 s. in its passage 
around the Sun. This is the Earth's yearly 
motion in its orbit. Mercury and Venus have 
no satellites or moons revolving about them. 
The Earth has one. Beyond the Earth's orbit 
is Mars with two moons. Beyond Mars the 
Asteroids, a collection of nearly 200 small plan- 
ets, not following one after another in a regular 
orbit, but each having its own orbit, being com- 
paratively near each other, and, from analogy^ 



Kendall's lunar telluric globe. 11 

it is a reasonable supposition that at some time 
a large planet with, two or three moons traversed 
this orbit. Beyond the Asteroids, Jupiter with 
fom^ moons, then Saturn with eight moons, 
and its system of rings, then Uranus with four 
moons and last Neptune with one. The meaji 
distance of Neptune is 2,775 milhons of miles 
from the Sun, about thirty times the distance 
from the Sun that we are. It is possible that 
still further away other planets may be dis- 
covered. This hst completes the planet fam- 
ily, and is called the Planetary System, and 
we can now study the further movements 
of the member in which we are most inter- 
ested. The shape of the Earth is spherical,, 
and is in round numbers 7,925^ miles through 
its longest diameter at the equator, and 
7,899 miles from pole to pole. This excess- 
of matter, some thirteen miles all along the* 
equator, will be remembered as an important 
factor, when we consider the subject of the 
precession of the equinoxes. Around its shortest 
diameter, called its axis, the earth rotates with 
a perfectly uniform motion once in 23 h. 66 m. 
4 s.; this is a siderial day. The extremities of 
this axis are called the poles, one the north 
pole, and the other the south pole. The axis 
of the Earth is inclined to the echptic at an 



12 Kendall's lunar telluric globe. 

angle of 23^ degrees. This will be often referred 
to, particularly as explaining change of seasons, 
etc. This inclination and the fixedness in the 
direction of the axis canses our globe to present 
itself to the Sun differently at different seasons 
of the year, turning the two poles alternately 
nearer the Snn. This angle produces changes 
of seasons exactly suited to the animal and 
vegetable life existing on its surface. These 
are also the causes which operate to vary the 
length of day and night in winter and summer. 
The Earth, hke the Sun, has a motion in a 
small orbit caused by its revolution about the 
common center of gravity of itself and the 
Moon, this point falls within the Earth's sur- 
face about one-fourth the distance from the 
surface to the center. The weight or gravity 
of the Earth is about 5.44 times as much as 
the same volume of water would be. 



THE MOON. 
The Moon is a small planet revolving about 
the Earth, the attraction of the Earth holding it 
in its orbit and reducing it to a satelhte, or at- 
tendant upon it in its progress around the Sun. 
If the Moon were once freed from the imme- 



Kendall's luxae tellueic globe. 13 

diate force of this attraction of the Earth, it 
would assume an independent orbit about the 
Sun. Its size is about one-fiftieth that of the 
Earth, its diameter 2,160 miles, and its mean dis- 
tance from the Earth 240,000 miles. In a little 
more than twenty-seven days it reyolves 
about the Earth in an elhptical orbit, its 
poles being shghtly inclined to its orbit. It 
revolves on its axis once while making a re- 
volution in her orbit, thus presenting the same 
face to the Earth at all times. This is a pecu- 
har feature of the Moon's motion, and as a re- 
sult we should never be able to see any of th^ 
Moon's surface except the half turned toward 
the Earth, if ahttle motion, caUed the Moon's 
hbrations, did not enable us at times to see a 
httle further beyond one-half, along the equa- 
torial regions, and a httle beyond the poles on 
account of its inchnation on its axis. We can 
see about six-tenths of the Moon's surface. 
The surface of the Moon is very broken, ex- 
hibiting remains of immense circular craters, 
some rising to the height of 2,000 feet. There 
are no traces of an atmosphere, or of hfe in any 
form; water there cannot be or the Sun's heat 
would disperse it in vapor which would produce 
an atmosphere easily observed by astronomers ; 
there being no air or water, there can be no 



14 Kendall's lunae tellueic globe. 

clianges taking place upon the Moon's surface. 
It shines or gives light by reflecting the hght 
of the Sun, the proportion of this reflected hght 
that we receive from the Moon is about 1-470-, 
000 part of the hght from the Sun. A very small 
amount of hght comes to us from the Moon 
twice reflected; from the Sun to theEarth, then 
to the Moon and back to the Earth. This is 
observable when it is neio moon and we see the 
-dark part of the Moon by the reflection from the 
Earth. The orbit of the Moon is inclined about 
•5 deg. to the echptic. Its phases, influence on 
the tides, and the echpses wiU be considered 
nnder proper headings. 

ECLIPTIC AND ZODIAC. 

The apparent path of the Sun through the 
heavens each year is called the Echptic, and a 
belt of 8 deg. in width on each side of the Echp- 
tic is called the Zodiac, from the pictures of an- 
imals with which it was decorated by ancient 
astronomers. This belt called the Zodiac is the' 
real path of the Earth about the Sun, and also 
of aU the other planets. The Earth is inchned 
to this Echptic at an angle of 231- deg., and the 
Echptic is represented on a globe by a great 
circle extending around the globe at an angle 
of 23J deg. to the Equator. We can better un- 
derstand this circle if we consider it extended 



Kendall's lunar telluric globe. 15 

indefinitely in space in all directions from the 
globe. 

To Set Up Kendall's Lunar Telluric Globe 
AS A Lunarian. 

Tlie Earth is represented by either an 
eight-inch or a six-inch globe, with the di- 
visions of land and water clearly printed, and 
all the great circles, isothermal lines, meridians, 
etc., usually shown on the best quahty of globes. 
The Moon is shown by a ball of wood one-half 
dark, and one-haK hght ; for the eight-inch globe 
it has a diameter of scarce two inches, a^nd for 
the six inch ball about one and one-half inches, 
thus preserving the relative sizes of the Earth 
and the Moon. To support the Moon is a rod on 
which it slides up and down at the will of the 
operator, held in any position on the rod by a 
spring. The Sun^ represented formerly by a re- 
flector, we now represent by a curved rod similar 
to the Moon support, but longer, and bearing a 
shding pointer to more clearly locate the direc- 
tion of the Sun's central ray as it strikes the 
Earth. In setting up the globe in any form, 
follow the cut, (on next page,) placing the 
Earth with its proper inchnation-arm on the 
short arm of the stand, the Moon on the 
long arm of the stand, and the Sun on the 
wood arm extension to the stand. The day 



16 



KENDALL S LUNAE TELLUEIC GLOBE. 



and night circle is not required in this instru- 
ment. 




m 
< 



To Set Up Kendall's Lunae Telluric Globe 
AS A Tellueian. 

Eemove the Moon and transfer the Earth to- 
gether with its inchnation-arm from the short 



KENDALL S LUNAK TELLURIC GLOBE. 



17 



arm to the long arm of the stand. Eemove the 
ivood arm extension to the stand and transfer 
the Sun from it to the short arm of the stand, 
.and press it down on the iron portion of the 
hub, leaving the nickel or brass portion to re- 
Tolve freely within the band of the Sun support. 
Hevolve the arm until the index pointer at- 
tached to the short arm indicates December 
21st, on the Zodiacal Circle. Then turn the 
inchnation-arm under the Earth parallel with 
the arm of the stand and pointing toward 
rthe Sun. This will throw the North Pole of the 
.Earth away from the Sun, (see cut) ; now adjust 




SET UP AS A TELLURIAN. 



18 Kendall's lunae tellueic globe. 

the day and night circle so that the highest 
part shall fall directly over the Arctic Circle at 
its nearest point to the Sun 23|- degrees from 
the North Pole. If the whole stand be lifted up, 
and without disturbing the relative positions 
of the Earth and Sun, the side of the stand 
marked June is placed to the north, the 
Earth may be revolved any number of times 
about the Sun, and the North Pole of the Earth 
will retain its position, pointing in the direction 
of the North Star. In the construction of the 
Tellurian, the most important feature to be 
shown is the yearly motion of the Earth 
about the Sun, as it illustrates the important 
phenomena of the change of seasons, varia- 
bleness in length of day and night, etc. The 
daily revolution of the Earth on its axis is not 
shown, except as the globe may be revolved 
with the hand. The independent Ecliptic is 
constructed by removing the thumb screw from 
the upright piece of the day and night circle, 
and using the piece thus loosened to complete 
the circle surrounding the globe parallel with 
its orbit. To set the pointer for the Sun at its 
proper height, revolve the globe to either of 
the Equinoxes and set the pointer directly over 
the Equator where it is crossed by the Ecliptic. 



Kendall's lunae tellueic globe. 19 



PEOPOSITION I. — CO:\IPAEATIYE SIZES OF THE SUN, 
EAETH AND MOON. 

( Lunarian.) 

With an eight-inch globe, the Moon is repre- 
sented by a ball a trifle under two inches in 
diameter, and vrith a six inch-globe by a ball 
about one and one half inches in diameter. The 
relative size of the Sun in each case can be 
rudely shown by supposing the cuiwed rod sup- 
porting the Sun pointer to be extended, and 
complete the circle of which it forms a part. 

Peob. — 1. "VvTiat is the radius of a circle that 
would represent the circumference of the Sun, 
if the Earth were represented by a ball six 
inches in diameter? x\ns. 28 feet. 

2. What is the length of a cii'cle represent- 
ing the ciiTumference of the Sun, if the Earth 
be represented by a ball eight inches in diam- 
eter? 

PEOPOSITION II. — EEYOLUTION OF THE MOON ABOUT 
THE EAETH. 

(Lunarian.) 

The Earth is shown on the short arm of the 
stand, and the Moon on the long arm. The 
Earth's position is not located in the center of 
the stand but at a distance to represent the 



20 Kendall's lunak tellukic globe. 

common center of gravity of the two bodies. 
This common center of gravity of theEarth and 
Moon is a point about one-fourth distant with- 
in the Earth from its surface to its center, and 
in about 27^- days the Moon revolyes about the 
Earth, the Earth in the same time describing 
a small circle abont this point within itself. 

In the article on the Moon we noticed that its 
orbit was incHned about 5 deg. to the Ecliptic ; 
in order to show this, we place the Moon on the 
rod support in order at a given position to shde 
it high enough to be 5 deg. above the Echptic, 
or again 5 deg. below the Echptic. Place the 
Moon near the top of the rod support with its 
white side to the Sun, revolve it once around 
the Earth, and note that this bright side has 
retained the same relative position to the Sun. 
Now explain that in this one revolution, its 
real orbit has been from the top of the support 
to the bottom of it in one-haK a revolution and 
back to the top again in the last half. 

Pbob. — 1. Where would be the point around 
which the Earth and Moon revolve, if the Moon 
were the same size and density as the Earth? 
x\ns. Midway between the two bodies. 

2. Where would this point be if the Moon 
were larger and heavier than the Earth? 



Kendall's lunak telluric globe. 21 
problem iii. — phases of the moon. 

( Lunarian.) 

In the last proposition, we showed the revolu- 
tion of the Moon about the Earth once in 27 J 
days : if this revolution be observed from a point 
of observation on the Earth, the phases of the 
Moon will be seen. From new moon to new 
moon again 2% days are occupied. This is not 
usually understood, from the fact that a revo- 
lution of the Moon is accomplished in about 27^ 
days, but the Earth's progress in its orbit is 
sufficient during the 27J days to require about 
two additional days to complete the phases. 
Eevolve the Earth on its axis, so that a given 
point. New York for instance, will be below 
the horizon, or the Sun will appear as set in the 
West. Then move the Moon to the side of the 
Earth toward the Sun, but a httle further 
above the horizon, and the crescent or bright 
circle of the neiv moon is seen from the position 
on the Earth selected. As it takes 29 days to 
again arrive at new moon, if we move the Moon 
forward in its orbit 1-29 the distance about the 
Earth, the phase of the next night is shown, 
viz : the crescent a trifle larger and higher above 
the horizon. This crescent will increase in size 
each night, until the seventh night the Moon is 
seen in its first quarter; continue the progress 



22 Kendall's lunar telluric globe. 

of the Moon until it is on the side of the Earth 
opposite the Sun, and the full moon will be 
shown, the whole surface illuminated by the 
Sun and in position to be seen from the Earth. 
The gibbous form of the Moon is shown be- 
tween first quarter and full moon, and again, 
after the Moon's passage of the point opposite 
the Sun and before the third quarter is pre- 
sented. 

Following the movement for a few nights be- 
yond third quarter, the crescent of the old 
moon is seen. The new moon is seen from our 
location on the Earth at sunset, and the old 
moon just before sunrise. The horns of the 
crescent of the new moon are pointed east, and 
of the old moon west. Also note that at all times 
one-half the Moon is illuminated by the Sun, 
while either no part or the least crescent of 
the illuminated portion may be visible from the 
Earth. This is always the case, except during 
an Eclipse. That the crescent appears more or 
less inclined, commonly called a ''wet or a dry 
moon," is shown by shding the Moon higher 
or lower on its support. 

In representing the phases of the Moon, we 
have shown all parts of its surface as turned to 
the Earth, in the course of each revolution. In 
our article on the Moon we stated that the real 



Kendall's lunar tellueic globe. 23 

motion is once on its axis at each revolution 
in its orbit, thus showing only one-half its sur- 
face to the Earth. To illustrate this, put the 
Sun rod on in place of the Moon; (it will fit 
over the hub, instead of in the hub,) slip the 
Moon from its support and put it on the Sun 
support and revolve it about the Earth, and the 
same side of the Moon will be turned to the 
Earth. The two can be combined by supposing 
the white part of the Moon to be a hght, or 
illuminated half of the Moon, and that it moves 
around as the Moon turns on its axis. 

Peob. — 1. In what position in its orbit is the 
Moon when we have the dark moon? Ans. 
Between the Earth and Sun. 

2. Where is the Moon, when we see it as a 
full moon? A. — It is on the side of the Earth 
opposite the Sun. 

PEOP. IV. — ECLIPSE OF THE SUN. 
(Lunarian.) 

In general terms an Echpse of the Sun is 
caused by the interception of the hght of the 
Sun, by the intervention of the Moon between 
it and the eye. It occurs at irregular intervals, 
and certain well known causes enable as- 
tronomers to calculate with the greatest ac- 
curacy for years in advance, just the date when 
each Echpse will occur, and on what part of the 



24 Kendall's lunar telluric globe. 

Earth the phenomena will be visible. To 
understand this clearly let ns make some ex- 
periments. Place the Moon at the middle of 
its support and revolve it about the Earthy 
and at each revolution it will intercept the 
Sun's rays or cast a shadow on the Earth;, 
evidently this is not correct. Move the Moon 
to the top of its support and revolve it, and 
its shadow will pass over the Earth, and there- 
would be no echpse, so at the bottom of its sup- 
port a shadow would be cast into space below 
the Earth; now we have previously learned 
that the Moon's orbit is inchned so that in each 
revolution it passes from the top of its support 
to the bottom and back again, therefore at 
some time in this revolution it would be the 
right height to cast a shadow on the Earth. 
"While the Moon is making this revolution the 
Earth is mo^dng rapidly forward in its orbit, 
and continually changing this point, and we- 
can thus understand that when the Moon 
passes between the Earth and Sun at a point 
which is at or near the plane of the Earth's 
orbit, its shadow will be precipitated upon the 
Earth's surface, and to all the inhabitants of 
the Earth within the boundaries of this shadow 
of the Moon there will be observable an Eclipse 
of the Sun. As the Sun is so much larger than 



Kendall's lunar telluric globe. 25 

the Moon, this shadow is cast in the shape of 
the fnistrum of a cone about 140 miles wide at 
the Earth; yarying, however, in proportion to 
the distance of the three bodies from each 
other at the time of the Echpse ; even in some 
instances the shadow does not reach to the 
Earth. To show this at night place a candle 
or lamp in place of the Sun pointer. 




ECLIPSE OF THE SUX. 

Echpse of the Sun illustrating the form of 
the Moon's shadow, and position of the Sun, 
Earth and Moon. 

Prob. — Can we have an echpse of the Sun at 
full Moon? Ans. No, it must occur in the dark 
of the Moon, as it occurs only when the Moon 
is passing between the Earth and the Sun. 

PROP. y. — ECLIPSES OF THE MOON. 
( Lunarian.) 

As the Moon is the nearest to the Earth of 
snj of the celestial bodies, of sufficient size to 
cast an observable shadow, it is evident the 
Moon is echpsed in some other way than hj an 
intervening body intercepting its hght. This 
Echpse of the Moon, then, must be the Earth's- 



26 Kendall's lunar tellueic globe. 

shadow seen on the face of the Moon, and it 
must occur when the Moon is on the opposite 
side of the Earth from the Sun, and conse- 
quently at full moon. For the same reasons as 
explained in connection with the Sun's Eclipse, 
it can be shown that when the Moon passes the 
point in its orbit on the side of the Earth oppo- 
site the Sun at a height nearly corresponding 
withtlib plane of the Earth's orbit, the Earth's 
shadow will be thrown upon the Moon, and 
that it is only in this position that an Echpse 
of the Moon can occur. 




ECIilPSE OF THE XOOX. 

Echpse of the Moon, showing relative posi- 
tion of the Sun, Earth and Moon and form of 
shadows cast by the Earth. 

Peob. 1. — If the Moon is some distance above 
the plane of the Earth's orbit at full moon, 
where will the shadow of tlie Earth fall? Ans. 
In space below the Moon. 

2. — How often does an Eclipse of the Moon 
occur? Ans. — At irregular periods, by reason 
of the Earth's motion, as explained in the 
Sun's Echpse, and for the same reasons the 



Kendall's lunar tellueic globe. 27 

Moon's Eclipses can be computed years in ad- 
vance of tlieir occurrence. 



PEOP. YI. — TIDES, 
(Lunarian.) 

This name is applied to the alternate rising 
and falling of the waters in the ocean, which 
occur at regular intervals twice each day. 
The causes of a tide in any body of water, is 
in the yielding character of the water itself, 
acted on by the attraction of the Sun and 
Moon. We notice further along that the cen- 
trifugal force generated by the revolution of 
the Earth and Moon around their common 
centre of gravity, also figures as a cause of 
some pecuhar features of the tides. Place the 
Moon directly between the Earth and the Sun, 
and the position of these bodies at the highest 
tide is shown, for in this position both the Sun 
and Moon with u.nited forces, are operating to 
draw the waters of the ocean to a point near- 
est them. In the cut, (following first on next 
page,) we see in this position of the Moon that 
the tide at A is a high tide. 

The tide at B we will consider presently. 
Eevolve the Moon to the side of the Earth 
opposite the Sun, and the high tide will follow 
the Moon to that side of the Earth, for the 



28 



KENDALL S LUNAR TELLURIC GLOBE. 



Moon is SO mucli nearer the Earth than the 
Sun is, that it exerts over three times the influ- 




SPBIXG TIDE. 



ence on the tides that the Sun exerts. In this 
last position the tide that was at B is now at 
A, and swelled by the Solar Tide, and the tide 
that was at A is now at B, less the Solar Tide. 
In either of these positions the tides are the 
highest, and are designated as Spring Tide. 
Eeyolve the Moon to quadrature, or at right 
angles to the Sun, and the Sun's attraction is 
no longer in a line with the Moon's, but is 
operating to lessen the real tide which is the 
lunar tide, and in this position the tide runs 
low and is called Neap Tide. 
In noticing the cut below, the tide D and 




NEAP TIDE. 



C is less than A and B in the former cut, be- 
cause its volume is reduced by the tide A and B 



Kendall's lunae telluric globe. 29 

in this cut, there being no tide at C and D at 
Spring Tide. 

The solar tide is noticed at about the same 
hour each day. The lunar tide falls back about 
fifty minutes each day. To illustrate this, let 
the instructor choose any shore he pleases on 
the globe, and then revolye the place se- 
lected, until it has passed the meridian of the 
Moon an hour or two, the effect of the Moon's 
attraction of the waters of the ocean would 
now result in bringing them roUing up against 
the shore selected, and the tide would begin. 
Suppose twenty four hours to elapse, and re- 
volve the Earth on its axis just one revolu- 
tion, and move the Moon forward in its orbit 
l-27th of the distance around the Earth, 
which it would have passed through while 
the Earth has been making its revolution 
on its axis, and you will see clearly that the 
Earth must move some further before the 
attraction of the Moon will cause the influx 
of the waters against the shore as on the day 
hefore. The solar tide is regular, because the 
Sun is not moving forward in an orbit, and 
the Earth presents a given shore to its in- 
fluence at regular intervals; whereas the 
Moon moves away while the Earth is revolv- 
ing, and the tides occur at proportionate 



30 Kendall's lunar telluric globe. 

intervals later each day. From our in- 
spection of the forces of gravitation on the 
tides, we have thus far explained why tides 
would occur once in twenty-four hours, but 
observation demonstrates that they occur once 
in twelve hours. In reverting to the cut of 
Spring Tide we see a reason for the tide at ''A" 
but no explanation of the tide at ^^ B." If we 
can explain the tide at B, and the tide at D in 
the cut showing Neap Tide, it will explain a tide 
once in twelve hours. In observing the tide, 
which follows twelve hours after the lunar tide, 
it is found that it varies in height but a small 
amount except from the accession or with- 
drawal of the solar tide. If we adopt the theory 
that the Moon draws the water from the sides 
of the Earth and heaps them on the side near- 
est itseK, and this simple taking away of the 
water at the sides leaves a surplus on the side 
of the Earth opposite the Moon, we must be 
assured of the fact that it is not a tide formed 
by a marked rise in the waters of the ocean, 
but an interval of high water from an absence 
of low water during that period. This does not 
appear to be the case, and the most reason- 
able explanation is the centrifugal force created 
by the revolution of the Earth and Moon 
around their common center of gravity. This 



Kendall's lunae tellueic globe. 31 

point, to be sure, falls within the Earth's sur- 
face, but the force generated is undoubtedly 
sufficient to cause the waters of the ocean to 
follow in obedience to it, and this would make 
a tide on the Earth's surface opposite the 
Moon's position at all times. 

The formation of the land has much to do with 
the height of the tides. At the Bay of Fundy 
it sometimes reaches the enormous height 
of sixty feet, while at other points it may be 
broken up by projecting capes, and amount to 
a rise of but one or two feet. The forces of 
gravitation act all over the surface of the Earth, 
and it is fair to suppose that there are tides in 
all bodies of water, but the influence is so 
shght that it is not measurable, except in the 
ocean, where it gathers power from the immense 
volume on which these forces are acting. 

Peob. 1. — What is centrifugal force? Ans. 
That force by which a body moving in a curve 
tends to fly off from the axis of motion in a 
tangent to the curve. 

2. — What would prevent the waters of the 
ocean flying off from the Earth's surface in 
obedience to this law? Ans. — The attraction 
of the Earth. 

3. — What is the ebb and flow of the tide? 



32 Kendall's lunar tellueic globe. 



PEOP. YII. — THE OEBIT OF THE MOON, AND ITS EEY- 

GLUTION monthly THEOUGH THE 

ZODIACAL SIGNS, 

( Lunarian.) 

As we look at the Moon from the Earth, its 
orbit is within the Zodiac, and as it makes a 
xevohition about the Earth in 27 J days, we ob- 
serve it passing through all the signs of the 
Zodiac each month. This orbit, if the Earth 
were standing still while the Moon made its 
Tevolution, would be as shown on the globe. 
But if we could take our place of observation 
on the Sun, the path of the Moon through 
space would be something hke this cut : 




MOON S PATH THEOUGH SPACE. 

From the first position, to the second posi- 
t^ion the Moon moves ahead of the Earth. 
Erom the second position to tne third position 
the Moon follows the Earth and completes the 
circuit, the Earth meanwhile having advanced 
one-thirteenth of the distance about its orbit. 

To exhibit this path of the Moon, it is more 
convenient to move the globe-stand along 
the edge of a table, and at the same time re- 



Kendall's lunar telluric globe. 33 

Yolve the Moon from first to second, to third 
position, as described. 

The Moon's orbit is always concave to the 
Sun, but no mechanical arrangement can well 
show this, as it depends on the immense dis- 
tance traversed by the Earth while the Moon 
is making a single revolution about it. If in 
the above cut we shonld draw a hne connecting 
the first position and the last position, in which 
the Earth is shown in the cut, and suppose it to 
be one month's, instead of two months' progress 
in its orbit, this hne at its widest part would 
be over a million of miles from the Earth's 
orbit, and would subtend or connect the ends 
of an arc about 40,000,000 miles in length. 
Now the Moon is but 240,000 miles from the 
Earth, and if it moves forward with the Earth 
so long a distance, while swinging from 240,- 
000 miles one side of the Earth to 240,000 miles 
on the other side, we can see that it cannot vary 
enough from the Earth's orbit to make any 
portions of the Moon's orbit convex to the Sun. 

Prob. — Draw a large circle on the black- 
board, and divide it into thirteen equal parts. 
Let the circle represent the Earth's orbit. 
What is the length of the circle ; what is the 
length of each part? Compare the Moon's or- 
bit with this circle. 

3 



34 Kendall's lunae tellueic globe, 
peop. viii. — annual movement of the eaeth 

AEOUT THE SUN. 
(Tellurian, without the day and night circle.) 

We give here a cut of a globe as usually 
mounted. 




It will be noticed that the motion possible 
in this form, is the rotation on its axis, or 
its daily motion, and that this is exhibited 
within the centre of the Zodiacal Signs. The 
impressions conveyed to the mind of a child 
in examining a globe thus mounted, must of 
necessity be erroneous. 

In the Tellurian form of our globe, we show 
the Earth's yearly revolution among the signs 
of the Zodiac, and around the Sun, and its 
motion on its axis at the same time. And ii 
there were no other features to recommend 
the Lunar Telluric Globe to the practical com- 



Kendall's lunar telluric globe. 35 

mon sense of teacliers, this simple arrange- 
ment would assist so materially in making 
clear to the minds of pupils, the proper motions 
of the Earth in causing changes of seasons, 
etc., etc., as to make it almost indispensable in 
the school room. Note in this revolution of 
the Earth that the north pole points in the 
same direction at all times; the Earth's axis, 
therefore, is shown as inclined to the Ecliptic 
at the proper angle. 

PROP. IX. — PARALLELISM OF THE POLES OF THE 

EARTH, 
( Tellurian.) 

This proposition, is the form of words gener- 
ally used, to convey the idea that the Earth's 
axis at any given time is parallel to its axis at 
any other time, or at all times. It is a self-ev- 
ident proposition, for if the Earth moves 
in a plane, and inchned to that plane at 
all times at a given angle, this angle must 
always remain the same. To make it clear 
and observable, remove the Earth from its 
stand, letting the inchne arm remain in the 
liub : insert in the inchne arm in place of the 
Earth, the Moon support or rod; note its inch- 
nation to the Zodiac at the base of the stand, 
and revolve to any other position and it will be 
seen that it is parallel to the position first 



36 Kendall's lunae telluric globe. 

noted. This is a very satisfactory experiment^ 
and assists materially in showing the causes 
operating to produce the change of seasons. 

PBOP. X. — plane of the ecliptic, parallel to 

THE earth's orbit. 
( Tellurian.) 

The geographical Echptic is shown on the 
globe by a great circle crossing the Equator at 
an angle of 23^- deg. The Sun is always direct- 
ly oyer this Ecliptic ; place it so on the globe 
and without reyolving the Earth on its axis 
revolve it in its orbit, and the Sun pointer will 
follow this Echptic throughout the year. If^ 
however, the Earth is turned on its axis, our hne 
on the globe moves away from the Sun pointer^ 
and this hne no longer represents the Ecliptic 
until a complete revolution is accomphshed. 

Let the horizontal part of the day and night 
circle represent the Echptic, or complete it by 
using the perpendicular part to complete the 
circle with, and then revolve the Earth in its 
orbit or on its axis, and we show the true 
motion of the Earth in the Echptic. The- 
orbit of the Earth is parallel to the Zodiac as 
laid down, our extemporized Ecliptic is also 
parallel to the Zodiac, as we can show by meas- 
urements or observation, consequently they 
are rarallel to each other. 



Kendall's lunar telluric gloee. 37 

PROP. XI AND XII. — the SOLSTICES. 
(Tellurian.) 

The word Solstice is so called from the ap- 
pearance of the Sun as standing still at this 
season of the year. There are two Solstices 
each year, — one in mid-winter, Dec. 21, and 
one in mid-snmmer, June 21. The former the 
winter Solstice, the latter the summer Solstice. 
The Sun appears to stand still at the winter 
Solstice, because it is the turning point of its 
course south of the Equator, and it begins the 
return passage up to the Equator, when an 
Equinox occurs, and on north to June 21, when 
the summer Solstice occurs, or it apparently 
turns and goes back towards the Equator. 
When over the Equator the autumnal Equi- 
nox occurs; the former Equinox is called the 
vernal Equinox. This passage of the Sun 
is all apparent, and not real, as is shown on 
the globe. On Dec. 21st let the sliding 
pointer of the Sun stand directly over the 
Echptic, marked on the globe, at its most south- 
erly point 23J deg. south of the Equator; see 
that the globe is in the correct position, with 
the north pole pointing aivay from the Sun to 
its full extent. Now revolve the Earth about 
the Sun and note the pointer follow up north. 



38 Kendall's lunae tellueic globe. 

across the Equator and 23j deg. north of the 
Equator, and then back to the place of starting. 

PEOP. XIII. — THE TEOPIC OF CANCEE. 
(Tellurian.) 

The Tropic of Cancer is so called from 
the fact that the Sun appears to us as 
shining from the constellation Cancer of the 
Zodiac, June 21st. Note the position of the 
Earth in the sign Capricornus, with the north 
pole inchned to the Sun; the position of the 
Sun pointer will be over the Tropic of Cancer. 
Eevolye the Earth on its axis and the Sun 
pointer will mark out this tropic in its whole 
path about the Earth. To an observer on the 
Earth the Sun will appear on the opposite side 
of the Zodiac in the constellation Cancer. 

PEOP. XIY. — THE TEOPIC OF CAPEICOEN. 
(Tellurian.) 

From the position noted in the last propo- 
sition, reyolve the Earth one-half a revolution 
about the Sun and it will be in the Constel- 
lation Cancer, and the Sun pointer will 
stand over the Tropic of Capricorn. Eevolve 
the Earth on its axis and the Sun's rays will 
exactly mark out the Tropic of Capricorn. 
The Sun now will appear from the Earth as in 
the Constellation Capricornus. The Tropic of 



Kendall's lunar tellueic globe. 39 

Capricorn is therefore the most southerly boun- 
dary of the region over which the Sun stands 
vertical, and the Tropic of Cancer its northern 
limit, and are each named from the Constella- 
tions in which the Sun appears at the seasons 
of the year when the extreme hmits of its ap- 
parent progress north and south is reached. 

PEOP. XY. — TOEEID ZONE. 

( Tellurian.) 

On June 21st, the Sun pointer will mark 
the Tropic of Cancer. Move the Earth slowly 
about the Sun three months in its orbit, and 
the pointer will stand over the Equator, 
which is one-half the distance across the 
Torrid Zone. Move the earth forward in its 
orbit three months more and the Sun pointer 
will indicate the Tropic of Capricorn, showing 
that in the total period of six months the Sun 
has apparently passed from directly over the 
Tropic of Cancer to the Tropic of Capricorn. 
Complete the revolution of the Earth and the 
Sun will return from the Tropic of Capricorn 
to the Tropic of Cancer, thus again traversing 
the width of the Torrid Zone. It must be re- 
membered that while the Earth has been mak- 
ing this annual revolution, it has completed 365 
revolutions on its axis, or about 183 times while 
the Sun moved from its northern to its south- 



40 Kendall's lunae tellueic globe. 

ern limit, and 183 times from its sonthern to 
its northern limit. It will be manifest that all 
points within the Torrid Zone have twice 
passed under the Sun's vertical rays during a 
single revolution of the Earth in its orbit. 

PKOP. XVI. — NO POINT ON THE EAETH's SUEFACE 

WITHOUT THE TOEEID ZONE, EVEE EEOEIVES 

THE sun's VEETICAL EAYS. 

( Tellurian.) 

As we have shown in proposition XY, the 
Sun appears to stop in its progress north at 
the Tropic of Cancer, and its southern limit 
is marked by the Tropic of Capricorn. The 
points in the temperate zone nearest to the 
Tropics at the proper seasons, will at mid-day 
observe the Sun nearly over the meridian, and 
the farther north or south from the Tropics, at 
which an observation is taken the greater will 
be the angle in which the Sun's rays reach the 
Earth, until the poles are reached, at which 
points the Sun will never appear above the 
horizon a greater distance than an angle of 23J 
degrees. 

The demonstration of this proposition on the 
globe needs no further explanation, as it illus- 
trates it clearly, by simply observing the posi- 
tion of the Sun, from any given point on the 
Earth at different seasons of the year. 



Kendall's lunak tellupjc globe. 41 
PEOP. xvii. — equal length oe day and night 

ON THE EQUATOE AT ALL SEASONS. 
(Tellurian.) 

For this reason the Equator is often called 
the equinoctial hne. On March 22nd, and Sept. 
22nd, the Sun is vertical over the Equator, and 
day and night equal at any point on the Earth; 
but at any point not situated on the Equator 
the length of day and night yaries, except at the 
above dates, in proportion as the Sun is distant 
from the Equator. In examining the globe, 
notice that a hne drawn from one arm of the 
day and night circle to the other, at a proper 
height to pass through the center of the globe, 
would divide the Equator into two equal parts 
at any season of the year, and that the hah 
toward the Sun is always on the day side, the 
other hall on the night side. Illustrate by tak- 
ing given places on the Equator, and set the 
glqj3e to different seasons of the year, and re- 
volve the Earth on its axis showing day side 
and night side ahke. 

PEOP. XVm. — LONGEE DAYS AND SHOETEE NIGHTS 

DUEING SUMMEE NOETH OF THE EQUATOE, AND 

THE EEVEESE SOUTH OF THE EQUATOE. 

(Tellurian.) 

Longer days and shorter nights during the 
summer north of the Equator, and the reverse 



42 KENDALL'S LUNAB TELLUKIC GLOBE. 

soutli of it, is explained from the fact that at 
this season of the year the North Pole is 
inclined toward the Snn, and the South Pole 
away from the Snn. The larger portion of 
the northern hemisphere is on the Sun side of 
the day and night circle, and the larger portion 
of the southern hemisphere is on the dark side 
of the day and night circle. Place the earth 
lit in position on June 21st, the North Pole will be 
inchned toward the Sun at its greatest angle 
23 J deg. EeYolve the earth on its axis, and 
note the large arc of a circle passed through 
on the day side of the day and night circle, in 
comparison with the small arc described on the 
dark or night side. As the Earth revolyes on 
its axis with a uniform motion, the length of 
these arcs will indicate the comparative length 
of the day and night. The reverse of these 
conditions may be noted in the southern hemi- 
sphere. By using the hour circle about the 
North Pole, an approximate measurement may 
be taken of the length of day and night, in any 
locahty, at any season of the year. 

Peob. 1. — In latitude 41 deg. north, what is 
the length of day and of night, June 21st? 
Ans. Nearly 15 hours day, 9 hours night. 

2. — In latitude 30 deg. north, what is the 
length of day, Dec. 20th? 



Kendall's lunar telluric globe. 43 

PROP. XIX. — shorter DATS AND LONGER NIGHTS 

DURING WINTER NORTH OF THE EQUATOR, AND 

THE REVERSE SOUTH OF IT. 

(Tellurian.) 

This proposition is simply the reverse of pro- 
position XYIII. Eevolve the Earth six months 
in its orbit to Dec. 21st, and the North Pole will 
be inchned 23^- deg. from the Snn, and the larger 
portion of the northern hemisphere on the 
dark side of the day and night circle. If the 
Earth be revolved on its axis in this position, a. 
given point, Chicago, for instance, will describe 
the smaller part of its revolution in the snn- 
light, while the greater portion will be passed 
through between sunset and sunrise. In illus- 
trating this proposition as well as the former 
one, we have placed the Earth in extreme posi- 
tions from the longest day to the shortest day. 
This change is gradual, each day decreasing 
in length from June 21st to Sep. 22d, when the 
day and night are equal, and either proposition 
can be illustrated by examples located at any 
point off the Equator. 

Prob. 1. — In latitude 41 deg. north, what i& 
the length of day, Dec. 21st ? x\ns. Nine hours 
and a few minutes. 

2. — In latitude 35 deg. south, what is the 
length of day and night, Sept. 2nd? Ans. 
Equal, 12 hours each. 



44 Kendall's lunae tellueic globe. 



PEOP. XX. — SIX MONTHS DAY AND SIX MONTHS NIGHT 

AT THE POLES. 

(Tellurian.) 

Place the Earth, in its position for Dec. 21st, 
revolve the Earth on its axis and note that all 
points within the Arctic circle have made a 
revolution without passing on the sun side of 
the day and night circle. In other words, on 
Dec. 21st, a day of 24 hours has passed, with- 
out any portion of the Frigid Zone turning into 
the hght of the Sun. Move the Earth for- 
ward in its orbit a month, and again revolve it 
on its axis, and no material change is observ- 
able, except a small part of the zone, farthest 
away from the pole reaches the sun hght. 
Move the Earth forward in its orbit two months, 
and the North Pole itself will appear under the 
day and night circle. It has been three months 
on the dark side of the day and night circle, 
and it will now continue six months on the sun 
side, and three months on the dark side to com- 
plete the year. It is only necessary to imagine 
the Earth revolving rapidly on its axis, while 
the Earth is moved about the Sun in its orbit, 
to make this illustration a very pleasing and 
interesting one. 



Kendall's lunar tellueio globe. 45 

prop. xxi. — the passage of the earth yearly 
through the signs of the zodiac. 

( Tellurian.) 

In considering the Earth as a member of the 
planetary system, we noticed that all the plan- 
ets have a motion about the Sun, and that their 
orbits are within the Zodiac. This fact is 
demonstrated by observation, as regards the 
other planets, and as we can see the Sun pass 
from one sign to another, in a year completing 
the whole circuit of the Zodiac, we could judge 
from analogy, that it was not the Sun moving 
around the Earth through these signs, but that 
the Earth itseh was moving around through 
the signs opposite, in the same manner as the 
other planets. It is not left to analogy, but in 
various ways has been demonstrated by astron- 
omers. One great difficulty with the ordinary 
style of globe mounting has been just this 
lack, viz., a motion around the Sun through 
the Zodiac. With our arrangement, the posi- 
tion of the Earth in the Zodiac can be read at 
a glance for any day of the year. The only 
explanation necessary, is to state that the 
pointer indicates the day of the month, and 
the Earth for that day is in the sign opposite 
the pointer. 

Prob. 1. — What is the Earth's position in 



46 Kendall's lunak tellueic globe. 

the Ecliptic on tlie 20th day of May? Ans. At 
the intersection of the constellations Saggeta- 
rius and Scorpio. 

2.— What on the 10th day of July? Ans. At 
the twentieth point in the sign Capricornus. 

PEOP. XXII. — THE APPAEENT PASSAGE OF THE SUN 

YEAELY THEOUGH THE SIGNS OF THE ZODIAC. 

( Tellurian.) 

In the last proposition we noticed that the 
Sun, as seen from the Earth, passes yearly 
around the heavens in the great circle of the 
Echptic, and is seen from the Earth, among all 
the constellations of the Zodiac. We have 
previously noted that the Sun hke the Earth 
does not revolve about its own geographical 
center, but is influenced by gravitation, and 
like the Earth revolves about a iDoint near its 
center. As a matter of convenience we have 
located this point the same distance from the 
center of the globe stand, in the Sun's position 
as in the Earth's, but if the Sun was placed 
exactly in the center of the stand, and the 
Earth moved about it, the same apparant pas- 
sage of the Sun through the signs would be 
seen by an observer situated on the Earth. In 
reading the Sun's apparent position in the 
Zodiac, the pointer indicates the day of the 
month and also the position of the Sun, as it is 



Kendall's lunae tellukic globe. 47 

in the sign, that designates the month and the 
day. 

Peob. 1. — What is the Sun's place in the 
Echptic on the 20th day of February? Ans. — 
At the second point in the Constellation Pisces. 
Why? Because on the 20th of February, the 
Sun is seen from the Earth as in this constel- 
lation in the heavens. 

2.— What on the 31st of October ? Ans.— At 
the ninth point in Scorpio. 

PEOP. XXIII. — change of seasons. 

( Tellurian.) 

The seasons are the four quarters of the 
year, as determined by the position of the Sun 
in the Echptic. They are usually designated 
as spring, summer, autumn and winter. As- 
tronomically, the seasons would be defined by 
the Solstices and Equinoxes, March 22nd, June 
21st, Sept. 22nd, and Dec. 21st, because these 
dates mark the position of the Sun as farthest 
north (summer), farthest south (winter), or over 
the Equator (spring and autumn). In practice 
the astronomical division is not adhered to, as 
the condition of the weather at the time of the 
year, whether hot or cold, wet or dry, has taken 
the precedence in fixing the division of the 
seasons. In England the warm weather of 



8 Kendall's lunar telluric globe. 

spring is eariier than with ns in the United 
States. The May day festival there is the be- 
ginning of summer, as the spring months 
there are February, March and April; May, 
June and July the summer months, while in 
this country the spring is later and the autumn 
extends a month beyond the corresponding 
kind of weather in England. In this compari- 
son we have taken two locations in the Tem- 
perate Zone, and find them to vary from the 
conditions of heat and cold. If we examine 
the Torrid Zone, we find the seasons marked by 
a very dry period, followed by a very wet period ; 
by tempests, hurricanes and protracted rain 
falls, or long periods of entire absence of rain, 
and consequent parched and blasted vegeta- 
tion, that corresponds with our winter seasons. 
Here the seasons are divided into two wet and 
two dry seasons, and two or three crops a year 
are often raised, at periods between the ex- 
tremes of the wet and dry seasons. There is 
no winter season here, for there is no ice or 
snow to melt. The Sun does not move off 
toward the horizon for six months, but con- 
tinually stands almost vertical and keeps the 
Earth always warm. To form some idea of the 
wet season in the Torrid Zone, Mr. Elliott, the 
meteorological observer of the government of 



Kendall's lunae telluric globe. 49 

Bengal, reports that during the month of Octo- 
ber the daily evaporation at that point is equal 
to two inches. The amount of heat absorbed 
by the conversion of this amount of water 
daily, over so large an area as the Bay of Ben- 
gal, is enormous, and roughly estimated would 
be equivalent to 300,000 steam engines of 1,000 
horse power each. Thus, while for one season 
the Tropical Sun is converting this vast quan- 
tity of water into vapor, and storing it in the 
clouds, at another season it is being precipitated 
in a deluge over the land. If we had to con- 
sider only the position of the Sun in the Echp- 
tic, it would fix June 21st as midsummer in the 
north Temperate Zone. We have other causes 
to examine. In looking into the phenomena of 
the Tide, we found that the influence of the 
Moon was not felt directly that it arrived at 
the Meridian of a given coast, it must pass that 
Meridian some distance, depending on the 
shape of the land, friction of the waters and 
such other causes as operate to prevent the 
water instantly running out of a river, because 
its mouth is lower than its source. It is so 
with the heat from the Sun. A longer or 
shorter winter has intervened since its last visit 
north of the Equator; masses of ice and snow 
have accummulated, the whole surface of the 



50 Kendall's lunar telluric globe. 

Earth in our latitude is frozen np, all this 
cold must be absorbed, or a large portion of 
the heat from the Sun be used up in melting 
the ice and snow, and preparing the way for the 
summer season, and this delays the seasons as 
we go north of the Equator. There are warm 
ocean currents and trade winds that assist in 
modifying the temperature at different locah- 
ties, but we find that the seasons are largely 
dependent in their character and in their 
changes upon the location on the Earth. Let 
us now take the globe and show the causes 
that produce the change of seasons in our own 
latitude. 

The Earth once each year revolyes around 
the Sun, with its axis inclined 23^- deg. to its 
orbit. Take a location in our latitude and note 
the position of the Sun from the location se- 
lected, and it will appear in summer as high in 
the heavens at mid-day, and in the winter south 
of the Equator and near the southern horizon. 
Also use the day and night ch'cle to show that 
in summer the Sun is above the horizon for 
more hours each day than in the winter season. 
Turn the Earth to Libra (March 22) and the 
Sun's rays will strike vertically at the Equator, 
obliquely in the north Temperate Zone, and 
almost horizontally at the North Pole. It is 



Kendall's lunae tellueic globe. 51 

-'this angle at which the rays of the Sun reach 
our position, together with the period in each 
day that the Sun is above the horizon, that 
makes the change of the seasons. As the Earth 
is moved forward, this angle, at which the 
Sun's rays reach our position, is changed. On 
June 21st, with the Earth in Capricorn, the 
Sun is 23J deg. north of the Equator, and the 
angle is lessened until the Sun appears almost 
'Over head in the heavens; it also shines more 
hours in the day than at any other season, and 
w^e have our summer. Sevolve the Earth 
six months to Cancer, and the Sun is now 
seen low in the southern horizon, 23^ deg. 
;south of the Equator. Its rays reach our posi- 
"tion more inclined than at any other season of 
'the year, and shine on us but a few hours of 
the day; it is our winter season. Let it be 
clearly understood, that the Sun pointer has 
not been moved up or down on its support to 
show the vertical rays of the Sun at the Tropic 
of Cancer in summer, and at the Tropic of 
Capricorn in winter, but the Earth's inchnation 
on its axis has presented these points on the 
Earth alternately to the Sun's vertical rays. 
The Sun's rays are no warmer in summer than 
in winter. 

The distance of the Earth from the Sun does 



52 Kendall's lunae tellukic globe. 

not enter as a factor in computing the heat of 
summer or the cold of winter. The inchnation 
of the Sun's rays, or the angle at which they 
reach the Earth at particular locahties, is the 
essential element to be determined; first, be- 
cause the larger the angle, the more space is 
covered by a given amount of heat from the 
Sun; and, second, the larger the angle, the 
greater the proportion of the Sun's heat is re- 
flected into space and dispersed. 

PEOP. XXIT. — YEENAL AND AUTUMNAL EQUINOXES- 
(Lunarian.) 

In considering propositions 11 and 12, we 
noted the apparent motion of the Sun from 
23^- deg. south of the Equator to 23^- deg. north 
of the Equator, and in this passage it crossed 
the Equator twice each year. It is directly 
over the Equator on the 22nd of March (the 
Yernal Equinox,) in its passage north, and 
on the 22nd of September, (the Autumnal 
Equinox,) in its passage south. These points 
are diametrically opposite to each other. "When 
the Sun is at these points, it is for an equal 
length of time above and below the horizon, 
and the days and nights are equal in both hem- 
ispheres. These points move slowly westward 
about fifty seconds annually, which is called 



Kendall's lunae telluric globs. 

the precession of the Equinoxes, and will be 
explained in the next article. It is only neces- 
sary to understand the above points to show 
them clearly on the globe, as one revolution of 
the Earth about the Sun traces the apparent 
path of the Sun correctly, and the index point- 
er denotes the day of the month on which the 
Sun crosses the Equator. The only care ne- 
cessary, is that the position of the Earth is 
correct at the beginning of the revolution. 

PROP. XXV. — PRECESSION OF THE EQUINOXES. 
(Lunarian.) 

A slow falling back of the Equinoxial points 
upon the plane of the Echptic, thus causing 
the Sun to arrive in either Equinox a httle 
earher than it otherwise would. This change 
is so shght that it cannot be shown on the 
globe, but the physical causes of it can be very 
clearly explained. In considering the shape of 
the earth, we noticed an excess of matter 
anound the Equator about 13 miles in thick- 
ness. If we place the Earth in such a posi- 
tion that the Sun stands directly over the 
Ecliptic, this mass of matter along the Equa- 
tor win be 23^- deg. above the line of the 
direct action of the attraction of gravitation 
of the Sun. This force acts on this mass of 



64 Kendall's lunae tellueic globe. 

matter, to pull it down to the nearest point ta 
it, and the Equator and Ecliptic would eventu- 
ally coincide, if it were not for the rapid revo- 
lution of the Earth upon its axis. As the 
result of these forces the poles of the Earth 
are slowly revolving about the poles of the 
Ecliptic. (Show this by turning the inclina- 
tion-arm about, v/ith the globe in it, without 
mo^dng the arm of the stand.) This motion is 
often explained, by calhng attention to the mo- 
tion of a top when its force is partly expended. 
The time occupied by a complete revolution of 
the pole of the Earth about the pole of the 
Ecliptic, is about 25,000 years. In illustrating^ 
exaggerate the motion, turning the inchnation- 
arm a half an inch or an inch ; then revolve the 
Earth about the Sun and show where the Sun 
crosses the Equator, and how much earlier or 
later you can make the Equinox occur, by any 
variation in the direction of the North Pole. 
At the time the first catalogue of the Stars 
was made, the North Pole was nearly 12 deg. 
distant from theTSForth Star. Its distance now 
is less than 1^ deg. In 12,000 years the North 
Pole will point to the star (Alpha) Lyrae. The 
seasons will change and follow this change in 
the direction of the NorthPole, as the Northern 
Plemisphere must be the coldest when the North 



Kendall's lunae tellubic globe. 55 

Pole is inclined furthest away from the Sun. 
This subject is an interesting one, as the time 
will come when the winter season will be when 
the Earth is farthest from the Sun, in its orbit, 
while now our winter occurs while the Earth is 
nearest the Sun. 





V 

In the above cut S T is the force of gravity 
exercised by the Sun. Y Z is the Echptic, and 
A B the Equator. The attraction of the Sun 
tends to draw the point A to Y, and therefore 
C to X, but the Earth's revolution on its axis 
results in moving C slowly about X. Illustrate 
this by moving the incHnation arm at D around 
its axis at Y. 

'• PEOP. XXVI. — SIDEEIAL TIME. 
(Lunarian.) 

Time is a period or part of duration. The 
period of time that we call a day is measured 
by the Earth's rotation on its axis. In order 
to determine when the Earth has made an ex- 



56 Kendall's lunab tellukic globe. 

act revolution, there must be an object from 
which to take our observations. When a day 
is measured from a str.r it is called a Siderial 
day and is of uniform length, 23 hours 66 min- 
utes and 4 seconds. The revolution of the 
Earth in its orbit does not alter the length of 
the Siderial day, because the fixed star from 
which the revolution is computed is so far dis- 
tant that the successive returns of that star 
to the meridian would be at equal intervals. 
To show a siderial day with the globe, take 
some object, distant the width of the room to 
represent the fixed star, then an exact revolu- 
tion of the Earth in its axis will bring any giv- 
en point on that globe under the meridian of 
that star, regardless of the position of the 
Earth in its annual revolution abont the Sun. 

PEOP. XXVII. — SOLAR TIME. 

Solar Time is a period of time measured 
by the apparent motion of the Sun, and a 
Solar day is measured by the Earth's rota- 
tion on its axis, as observed from the Sun, 
instead of from a fixed star. The Solar day is 
variable in length. By reason of the revolu- 
tion of the Earth around the Sun, the Sun 
apparently travels east- ward among the stars 
about twice its own breadth each day, and to 



Kendall's lunae telluric globe. 57 

record a Solar day the Earth, has not only to 
make a complete revolution on its axis, but 
enough more than a revolution to overtake 
this apparent motion of the Sun. Again, as 
the Earth during the winter season moves in 
its orbit faster than in the summer, the apparent 
motion of the Sun will be greater in the win- 
ter, consequently the time occupied by the 
Earth to bring the meridian of any given point 
under the Sun will vary in length. To illus- 
trate this on the globe, let the Sun pointer 
indicate a given place, say the Sandwich 
Islands, and without moving the arm revolve 
the globe once on its axis, and the pointer will 
indicate the Sandwich Islands. Now move 
the Earth forward an inch in its passage about 
the Sun, and suppose that the Earth has made 
a revolution on its axis, while proceeding for- 
ward in its orbit the distance moved, the Sand- 
wich Islands will now appear some distance 
from the pointer, and this distance indicates 
the part of a revolution that the Earth must 
make, in excess of one complete revolution, in 
order to mark a Solar day. We may call this 
a Solar day in the summer. If we should 
move the Earth three inches forward in its or- 
bit, we show a much longer period to make up 
the difference between a Siderial and a Solar 



58 Kendall's lunar telluric globe. 

day in the winter season, and the average be- 
tween these extremes of Solar time is called 
Mean or Clock time. The difference between 
the time by the clock and the time by the Sun, 
is called the equation of time. Four times a 
year the equation of time is reduced to noth- 
ing, and twice a year it amounts to 16 minutes. 

PROP. XXYIII. — MEAN, OR CLOCK TIME. 
( See Pro]position xxvii.) 

PROP. XXIX. — DIFFERENCE IN TIME AT DIFFERENT 

POINTS ON THE EARTH 's SURFACE. 

(Tellurian.) 

Use as an ordinary globe, with this advantage, 
i, e, of two places selected the difference of 
time on a given date can be shown, and also 
the position of the Sun. Ceylon and New York 
in December are north of the Sun; in June, 
Ceylon is south and New York north, etc. 

PROP. XXX. — AN INDEPENDENT ECLIPTIC, SHOWING 

THAT THE ROTATION OF THE EARTH ON ITS AXIS 

MOVES THE POINT AT WHICH THE ECLIPTIC 

CROSSES THE EQUATOR ENTIRELY 

AROUND THE EARTH EACH DAY. 

In our instructions '^ to set up Kendall's 
Lunar Telluric Globe as a Tellurian," we noted 
the manner in which the Independent Echptic 
is formed from the day and night circle ; tm^n 
the Earth on its axis, until the Geographical 



Kendall's luxak tellueic globe. 59 

Ecliptic on tlie globe is in the same plane as- 
the Independent Ecliptic thus formed, and the 
Sun pointer will follow tliis plane through the 
Earth's yearly motion in its orbit. EeYolve 
the Earth on its axis, and the points at which 
the Equator crosses the Independent Ecliptic 
wiU move about the Equator at each revolu- 
tion. 

PEOP. XXXI. — THE EEASON THE SUN SHINES ON THR 

NOETH SIDE OF BUILDINGS IN THE SUMMEE 

SEASON IN OUE LATITUDE. 

In the summer season the Sun rises and sets^ 
north of the east and west hne of any given 
point in the United States. Set the Earth in 
position June 21st, revolve it on its axis until 
New York is under the day and night circle,, 
its east and west hne will be designated on the 
globe by the parallel of latitude 40 deg. north 
of the Equator, and the dii'ection of this hne 
for an inch or two would carry it, if extended, 
some distance south of the Sun. Revolve the 
position selected to Sun-set and the same facts 
will be shown, i, e, the Sun above or north of 
the east and west hne of the place, and there- 
fore, shining for a time after Sun-rise, and be- 
fore Sun-set from north of the given place. 
At mid-day New York would be some 18 deg. 
north of the Sun, as the east and west hne is a 



60 Kendall's lunak tellukic globe. 

<3uryed line inclined to the Sun in summer and 
away from it in winter. 

PEOP. XXXII. — THE REASONS FOE THE DIVISIONS OF 

THE EAETH's SUEFACE INTO FIVE ZONES, — TWO 

FEIGID, TWO TEMPEEATE AND ONE TOEID. 

( TeUiiriaii.) 

There are physical reasons for this division, 
and it will be noted that the Tropic of Cancer 
is 23^ deg. north of the Equator and the Arctic 
Circle is 23^- deg. from the North Pole, and 
ihat this distance corresponds with the num- 
ber of degrees that the Earth's axis is inchned 
iiO the Ecliptic. Inasmuch as the North Pole 
is inclined from the Sun at one season of the 
year the same distance that the South Pole is 
inclined from the Sun at the opposite season of 
the year it follows that the change of seasons, 
^nd the difference in length of days in the 
Arctic Eegion is similar to the corresponding 
season in the Anarctic, and there must be two 
Frigid Zones. The position of the Arctic Cir- 
cles 23J- deg. from the poles is defined by the 
physical condition v/hich makes this point the 
extreme distance to which the Earth can re- 
volve without the Sun appearing above the 
horizon. The position of the Tropic of Cancer 
23^ deg. north of the Equator is defined by its 
b)eing the northern boundary over which the Sun 



Kendall's lunar telluric globe. 61 

stands vertical. The Zone indicated between 
the Tropic of Cancer and the Arctic Circle, 
called the Temperate Zone, has a corresponding- 
zone in the southern hemisphere for the same 
reasons that there is an Antarctic Eegion corres- 
ponding with the Arctic. These Zones then are 
not arbritary divisions, but are defined by the 
manner in which the Sun's rays fall upon them, 
either vertical as in the Tropical Eegions, more 
or less inclined in the Temperate Eegions, or 
not at all in certain seasons in the Frigid Zone 
within the Arctic Circles. These divisions are 
clearly shown on the globe, as the day and 
night circle in December 21st just touches the 
Arctic Circle, and shows the whole of the north 
Frigid Zone on the night side, or in darkness, 
and the Sun pointer traverses in the course of 
a year exactly the width of the Torrid Zone. 

PROP. XXXIII. — THE ARRANGEMENT OF AN AXIS FOR 
THE EARTH PEPENDICULAR TO ITS ORBIT, SHOW- 
ING THE SUN ALWAYS OVER THE EQUATOR, 
DISTINGUISHING THE CHANGES 
OF SEASONS, ETC, 
( Tellurian.) 

Eemove the inchnation arm supporting the 
Earth, and set the Earth in the hub in the place 
occupied by the inclination arm, place the Sun 
pointer over the Equator; if the Earth is now 
revolved about the Sun the pointer will follow 



62 Kendall's luxae tellueic globe. 

tlie Equator throiiglioiit the reyoliition. It will 
readily be seen that there can be no change 
of seasons. The rays of the Sun falling di- 
rectly over the equatorial regions every day 
throughout the year would render either ani- 
mal or vegetable life impossible from the ex- 
treme heat, and the scattered rays reaching the- 
2)oles could not warm into active life the germs 
hurned beneath the mouniains of ice. So to, if 
the day and night ciixle be placed into position, 
it will be seen that all days and all mghts are of 
equal length on all parts of the Earth, clearly 
demonstrating the wisdom displayed in the ar- 
rangement of our planetarj' system, that even so 
small a thing, as the slightest variation in the 
inclination of the axis of the Earth, might ren- 
der the greater portion, or even the whole 
Earth uninhabitable. 

PEOP. XXXIV. — A poixtee aeeaxged to be set foe 

AXY DAY OF THE TEAE, WHEN THEEE MAY BE BEAD 

AT A GLANCE, THE POSITION OF THE SUN IN THE 

ZODIAC, POSITION OF THE EAETH IN THE 

ZODIAC, COMPAEATIVE LENGTH OF DAY AND 

NIGHT, THE SEASON OF THE YEAE, AND 

IN FACT ALL THE EELATIONS OF 

THE EAETH TO THE SUN ON THE 

PEECISE DAY INDICATED. 

This pointer is attached to the short arm of 
the stand, and reaches down to the Zodiacal 



Kendall's lunar telluric globe. 63 

Circle. It is used in setting the Earth in a given 
sign of the Zodiac; in locating the day of the 
year by the position of the Sun in the Echptic ; 
and in fact is the index finger that is turned to 
the great clock dial of the Heavens, and in 
miniture, marks the changing seasons like the 
hour hand of a watch. 

With an ordinary globe it is necessary that 
the memory be charged ^Yith the exact location 
of the Earth and of the Sun at all seasons, in 
order to set it in position to represent these 
positions to a class, with this globe when once 
set up, it is only necessary to moYO the index 
pointer to the day or month in question and the 
problem is solved. 



MISCELLANEOUS. 

DECLINATION. 

The distance of an object from the Celestial Equator, 
measured on the meridian passing through it is called its 
declination. To find the Sun's declination on any day of 
the year, set the Tellurian with the Sun over the Autum- 
nal Equinox, Sept. 22nd; revolve the Earth to the day of 
the month selected, and the Sun pointer will indicate the 
distance north or south of the Equator over which it stands 
vertical. To measure this distance in degrees, turn the 
Earth on its axis until the analemma is under the Sun 
pointer, and read ofi the degrees. This will be the Sun's 
north or south declination on that day. ^ 

The Moon^s declination is reckoned from the Ecliptic, 
the same as the declination of the Sun is reckoned from 
the Equator. 



64 Kendall's lunak tellueic globe. 

EXAMPIiES. 

L— What is the Sun^s declination on the 20th of October? 
Ans. 11 deg. south. 

2.— What is the Sun^s declination May 3rd? Ans. 16 
deg. north. 

3.— What is the Sun^s declination Sept. 22nd? Ans. No 
degree. Why? 



ANTIPODES. 

TO FIND THE ANTIPODES OF A GIVEN PLACE. 

Set the Earth at either Equinox ; turn the given place 
under the day and night circle^ and take note of the num- 
ber of degrees it is located north or south of the Equator. 
If north of the Equator, the place under the day and night 
circle an equal number of degrees south of the Equator,, 
will be the Antipode of the place selected. 



CONCLUSION. 

We might largely increase the foregoing list, but have 
confined ourselves to important points that can be more 
clearly and more quickly explained with this apparatus 
than in any other way. To teachers who have given these 
matters much attention, the globe is a continual revelation 
of new and simple methods of explaining the most difficult 
problems relating to these three important members of our 
planetary system. It is however, a difficult task to make a 
clear exi^lanation of certain facts in writing, that would 
appear simple when shown by illustration ; and we hope 
all teachers who use the globe, will depend as little as pos- 
sible on the hand book. Read the facts as laid down in any 
good work on Astronomy, and as you read apply to the 
principles evolved by the globe, and thus secure your own 
solutions. For the benefit of those who have no suitable 
Astronomy to refer to, we would recommend Steele's Four- 
teen Weeks in Astronomy, advertised by A. S. Barnes & Co., 



THE STORY OF THE STARS, 

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J. DORMAN STEELE, Ph. D. 

This work was issued twelve years ago, and has secured a firm foothold 
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certain points of excellence which are not claimed by any of its numerous 
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1. The Introduction, giving the History of Astronomical Discovery, in- 
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2. The book is arranged systematically, thus facilitating both study and 
recitation. Under each of the PLANETS the order of topics is, (1) Descrip- 
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sons upon the Earth. This is followed by a clear and easily apprehended 
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